Open up your video-editing software program. Click on the "File" button, then click on "Import." Locate the video clips you want to use in your project and click "Add."
Click on one of the imported video clips and drag it onto the "Video 1" track. This will place the clip on the timeline for editing.
Click on a second video clip and drag it onto the editing timeline in the "Video 2" editing track. Click on the "Video 1" track so that it becomes highlighted. Click on the word "Motion" and click on one of the corners of the clip's frame. This will scale it down to the size you desire.
Click on the video clip in the "Video 2" track and adjust the scale size of the video so that the video in track 1 will fit in the frame of video clip 2 without completely overshadowing the video. This will give it a picture-in-picture feel.
Save the project. Click on "File," then click "Render" to make your multi-track video.